In the field of stump cutting machinery of a trailer type, it has been common practice to employ a gas- or diesel-powered engine to which drive shaft is fixedly attached a series of belts and pulleys to rotate a cutting wheel. The engine is mounted so that it rests generally centrally relative to the width of the frame, as does the cutting wheel. The desired result of such mounting is the promotion of a weight balanced apparatus. However, when a standard gas or diesel-powered engine is so oriented, it results in a substantial offset of the distal end of the engine's output shaft relative to the position on the cutting wheel shaft where a pulley might most suitably be mounted in order to accept the driving belts. Hence it is necessary to connect the output shaft to the cutting wheel using this combination of belts and pulleys.
In the interest of safety, the fewer exposed or potentially exposed moving parts of high power and speed in an invention, the more desirable an invention is. In the case of the aforementioned common practice, a number of high velocity belts and pulleys can be exposed by safety guards partially or fully removed out of necessity or neglect presenting a very true danger to the operators, as loose clothing, long hair, tools, and human body extremities are all candidates for becoming engaged in the moving parts.
An additional hazard associated with some of the aforementioned exemplary art devices is that the method of lowering the cutting wheel is caused by lowering of the entire deck. The nature of cutting stumps with such devices, results in particles of the tree stump, being forcibly displaced under the deck, where they accumulate throughout the process, resulting in the interference of the apparatus deck or guarding. These stump cutting units require a specially made skirting which can touch the ground at the maximum deck height yet adequately flex during the lowering of the deck, in order to deflect moving chips liberated during the cutting process. This hazardous condition is perpetuated if the protective skirt is not readily replaced after becoming damaged or worn.
A further danger often associated with high powered devices is the presence of a high speed toothed cutting wheel, particularly as it relates to stopping the cutting wheel should a dangerous situation arise and immediate shutdown is desired. In such a situation, stopping the cutting wheel quickly rather than gradually can mean the difference between non-incidence and injury. Many varieties of prior art devices, particularly those of chain and/or belt drive, provide no means of sudden deceleration of the cutting wheel whereas rather, a high amount of inertia being involved, the cutting wheel continues rotating at a high velocity.
Also, prior art devices routinely require the moving of the entire engine toward and away from the cutting wheel to loosen or tighten the belts driving the cutting wheel for the purpose of starting or stopping the cutting wheel.
In order to move the entire engine, as aforementioned, it has customarily been mounted on sliding members directly beneath the engine itself, which requires that the engine be located at a higher elevation than it would otherwise be necessary. This intensifies the normal vibrations associated with the operation of cutting stumps.
Additionally, a severe eccentric load is imposed upon the engine drive shaft bearings when a belt is tensioned radially against the diesel engine enough to positively force, rotatingly, cutter teeth through multiple types, conditions, and densities of wood and soil, resulting in rapid wear of the engine output shaft bearings and thus premature failure of the same.
The traditional method of driving the cutting wheel, as described above, allows the engine to be mounted only in a position which is cross-axial relative to the length of the apparatus frame. Such a restriction imposes axial stresses during operation which would be better applied side-to-side in the interest of minimalizing stresses imposed upon the frame.
The aforementioned exemplary prior art devices posses only limited capability to vary the cutting wheel speed without a significant loss of horsepower. Under certain cutting circumstances, such as in restricted access areas surrounded by fixed valuables, fine control might be attained by a slower cutting wheel revolution, as certain vibratory motions could be thus reduced. Also certain testing, such as tooth sharpness and hardness and shaft straightening requires slow, controlled revolutions with high torque.
A range of prior exemplary devices, as aforementioned, utilize a method of lowering the cutting wheel by a motion which lowers the entire deck, as the height of the cutting wheel relative to the deck and apparatus main frame is fixed. Although a simple and otherwise effective means of lowering the cutting wheel, the method here under consideration owns a certain limitation whereby space that is used for the accumulation of wood particles as they are removed from the remaining stump becomes reduced as the cutting wheel and resultingly the apparatus deck is lowered in the process of stepping the height of the stump down until it is appropriately below grade. This consequence requires special maneuvering of the cutter when cutting on larger stumps, as the accumulation of the wood particles impedes full lowering of the apparatus frame, deck and cutting wheel.
Based on the deficiencies found in the prior art devices, Applicant's invention is herein presented.